This invention relates to a centrifugal lubricant pick-up tube of the type suitable for use in hermetic motor-compressors, and in particular to such a tube which includes means for preventing foreign particles entrained in the lubricant from being circulated through the lubricant passageways of the compressor.
In hermetic motor-compressors, which are sealed units, the bearing regions are often lubricated by means of a lubricant pick-up tube, which is rotated about its longitudinal axis and has one end immersed in the compressor lubricant sump. The tube is mounted on the drive shaft of the compressor and exerts a centrifugal pumping action on the lubricant which flows through the lower open end of the tube. The tube propels the lubricant upwardly by means of centrifugal force to passageways in the shaft, which ultimately lead to the bearing regions of the compressor. The lubricant may contain foreign particles and contaminants left in the compressor during the manufacturing and installation process, and also particles deposited by the gradual wearing of the working parts during operation of the compressor. If these foreign particles are allowed to pass through the lubricant passageways and into the bearings, the bearings will wear rapidly and result in a reduced operating life of the compressor.
Prior lubrication systems used with hermetic compressors of this type generally provide a trap to separate the foreign particles from the lubricant, and to prevent these particles from circulating through the compressor with the lubricant. U.S. Pat. No. 3,049,285 contains a die cast oil lifting device which includes a lubricant passageway in communication with the circumferential pocket. Foreign particles are deposited in this pocket by centrifugal force. U.S. Pat. No. 3,692,435 discloses an oil lifting device comprising a revolving shaft which extends vertically into the lubricant and has a lubricant passage bored therethrough. Either a machined step portion or an insert is used to block the foreign particles from proceeding upwardly in the lubricant passageways.
U.S. Pat. No. 3,674,382 discloses a revolving shaft with a lubricant passageway, and having a portion of the shaft cut away. The cut-away portion is in communication with the lubricant passageway, and is enclosed with a ring-sleeve to define a receptacle for the foreign particles. These prior art devices are expensive to manufacture due to the particular die casting or machining required. Additionally, their use is limited to these compressor systems compatible with the particular die cast dimensions employed. U.S. Pat. No. 3,560,116 discloses a hermetically sealed motor-compressor unit in which the motor and the compressor are each cooled by separate oil flows. This patent includes a pick-up tube having an annular protuberance at its upper end that contains openings 48 on the upper portion of the protuberance. The compressor is cooled and lubricated in the normal manner by way of lubricant being propelled upwardly by centrifugal force through the pick-up tube and into the compressor bearing regions. An independent flow of lubricant passes through openings 48 to cool the stator. Openings 48 would likely allow foreign particles to accompany the lubricant which passes through opening 48 to the stator, thus causing the bearings to wear rapidly and also to reduce the operating life of the unit.
It is therefore desired to provide a pick-up tube for removing foreign particles from the lubricant supplied to a hermetic compressor that overcomes the disadvantages found in the prior art. It is further desired to provide such a pick-up tube that is efficient in operation and does not require costly machining or die casting of the drive shaft or oil lifting mechanism.